This invention relates to tractors and trucks particularly to the drive mechanism therefor. More particularly, this invention relates to an improved arrangement for pre-loading the bearings of the final drive or sprocket found in such final drive mechanisms. While the following discussion refers to the application of the invention to drive mechanisms for tractors and trucks, it is to be understood that such is merely for the sake of convenience. The invention has broad application as a mechanism for pre-loading bearings.
Tractors extensively used in the earthmoving industry typically include right and left final drives for transmitting power from the engine to the right and left track assemblies or wheels. Each final drive includes a drive sprocket or wheel journalled to a cross-shaft. The shafts are supported by bearings which include an arrangement or means for pre-loading the bearings supporting each shaft in the assembly which supports each shaft and sprocket with respect to its support housing. Also included is a retaining ring which abuts a reaction hub, which in turn bears on a bearing.
Previously, the bearings, which were spaced by a sleeve, were pre-loaded by means of securing the retaining ring for the reaction hub directly to its respective bearing. In order to provide the proper pre-load to the bearing with the prior art arrangement, the length of the sleeve between the bearing as well as the width of the reaction hub are two critical dimensions which must be accurately set. This, of course, presents a problem in manufacture, etc., and the additional costs incident thereto.
In addition, the reaction hub is splined to a large support hub for the final drive which allows a limited degree of torsional rotation caused by the change of rotational direction, e.g., shifting from forward to reverse, because of manufacturing tolerances incident to production of such structures. The relative torsional rotational movement is produced as power is introduced to the drive shaft for the planetary. As power is cycled during forward to reverse operation, bending stresses are built up in the plurality of bolts on a bolt ring which serve to retain the reaction hub, which often causes premature failure of the parts. This cycling also produces another deleterious effect in the form of galling of the metal of the reaction hub and bearings at their contact surface. It is to be a solution of these and other problems that this invention is directed.